How to Grow and Care for Anise Hyssop

Contrary to its common name, anise hyssop (Agastache foeniculum) is not anise or hyssop, though it is also a member of the mint family. Its leaves give off a subtle scent similar to anise, though some compare the scent more to basil or French tarragon.

The plant's flower spikes are typically blue-lavender to purple, depending on the variety, on upright stems adorned with dull green leaves. Each leaf is four inches long with toothed margins akin to the aesthetic of common mint.

This clump-forming perennial is native to parts of the Midwest and the Great Plains. It blooms abundantly from mid to late summer through early fall, attracting bees, butterflies, and hummingbirds. Their extended bloom period makes them good for cut flowers and mass plantings.

Botanical Name	Agastache foeniculum
Common Name	Hyssop, blue giant hyssop, lavender giant hyssop
Plant Type	Herbaceous, perennial
Mature Size	2-4 ft. tall, 1-3 ft. wide
Sun Exposure	Full sun
Soil Type	Moist, well-draining, sandy
Soil pH	Neutral
Bloom Time	Summer, fall
Flower Color	Purple, blue
Hardiness Zones	3-8 (USDA)
Native Area	North America

Anise Hyssop Care

Plant anise hyssop in spring after the last frost. Establish seedlings any time until early summer. Space 18 to 24 inches apart in borders, wildflower gardens, herb gardens, or butterfly gardens (or as specimens in containers).

These plants serve well in the middle or the back of perennial borders. Pair with companions such as Japanese anemone, brown-eyed Susan, goldenrod, or with fellow herbs like garlic, chives, oregano, and thyme.

Light

Anise Hyssop prefers full sun. It may grow in partial shade but will get lanky without enough sunlight.

Soil

Anise hyssop will do best when planted in soil that is fertile and well-drained. Do your best to avoid soil that is too heavy, which can make it difficult for the roots to get established and may lead to root rot.

Additionally, your soil should have a pH that is as close to neutral as possible. You can amend it with lime if it's too acidic.

Water

Water newly planted anise hyssop weekly, if there is no rainfall, for the first four weeks. Water slowly and deeply, welcoming deep, spreading roots. Once plants are established, cease watering. This perennial is drought-tolerant.

Fertilizer

Feed anise hyssop in early spring every other year, with organic compost that has been sprinkled around the base of the plant. Make sure to target the roots and leave a couple of inches of soil space between the compost and the plant's main stem. You can also use all-purpose fertilizer.

Types of Anise Hyssop

There are many types of anise hyssop and other similar plants within the Agastche genus. Bloom colors of various hybrid varieties range from pink to creamy white, powder blue to red-violet. Foliage can be dark green to lime green. Here are some of the most popular varieties:

• ‘Alabaster’ is a hybrid with creamy-white flowers. The foliage is lighter green than most other hybrids. Plants grow about 3 feet tall and not as bushy as some other kinds of anise hyssop.
• 'Black Adder’ has dark buds and red-violet flowers. It grows less quickly and robustly than other species.
• ‘Blue Blazes’ is a tall hybrid ofA. foeniculumandAgastache‘Desert Sunrise.’ Hardy to USDA Zone 5, this hybrid has pinkish calyxes and lavender purple blooms that seem to glow in the sunlight.
• 'Blue Fortune' is a sterile hybrid of A. foeniculumandA. rugosa. Flower spikes are especially thick and come in a shade of powder blue. Leaves are large and deep green. Peak bloom is in midsummer. Flowers last a particularly long while because they set no seeds. Plants grow 3 feet tall.
• ‘Blue Fountain’/’Blue Spike’ is another variety of anise hyssop to consider. This one has clear blue flowers.
• ‘Golden Jubiliee’ has lasting, powder blue flowers, contrasting pleasingly with its chartreuse foliage. This tough plant thrives even in high heat and humidity.
• 'Liquorice Blue' has violet-blue flowers with reddish-purple calyxes.
• ‘Purple Haze’ produces flowers spikes that are narrower than many other varieties of anise hyssop. Because they are so narrow, spikes do not attract as many large native bees, but they may be attractive to smaller pollinators that are able to fit inside.
• ‘Red Fortune’ has pink flowers. This hybrid does not attract as many pollinators.
• ‘Snow Spike’ (also known as ‘Album’) produces white flowers and grows 3 feet tall.

Pruning

Anise hyssop is a fairly independent plant and won't need much attention once it has established itself in your landscape. Occasional pruning can help encourage the plant to bloom and keep the plant looking its best.

Pruning is best done in early spring, using a pair of clean pruning shears. Cut back up to one-third of the plant to encourage more full, bushy growth. Remove any dead plant material just above a promising bud node.

Propagating Anise Hyssop

Every three to five years, you can dig up the plant and divide it. This will help prevent the center from dying out and rejuvenate the entire plant.

1. Divide the plant in spring by digging up the clump and dividing it in half.
2. Replant the division at the same depth as the original planting, at least 2 feet away from the original planting.
3. Water both plants well until re-established.

Common Plant Diseases

Be mindful that crown/root rot may occur in poorly drained soils. Keep an eye out for rust, powdery mildew, and leaf spots. Despite these potential issues, anise hyssop is quite hardy, being deer-resistant and a generally vigorous perennial.

From: thespruce